The invention relates to powder pencil leads, used in particular for cosmetic pencils and powder chalks. The latter are also known as soft pastel chalks. A cosmetic pencil provided with a lead in the form of a shaped body with porous composition that consists of mica, magnesium myristate as adhesion promoter and bentonite is described in DE 25 40 877 C2. A mica-containing and talcum-containing powder pencil lead, which contains spherical cellulose powder as binder, is known from reference EP 0 432 279 A1. In the same way as gypsum-containing leads (U.S. Pat. No. 4,624,273) or tri-calcium phosphate containing leads (DE 33 47 756 C2), these leads also have a porous composition. Owing to their low mechanical strengths, the production of these leads is problematic because the danger of a lead breakage is very high. A further disadvantage is that the leads break easily during the application to the skin and during the sharpening and have a tendency to crumble.
Thus, it is the object of the invention to propose a lead for cosmetic powder pencils and powder chalks, used for cosmetic purposes or for pastel drawings on paper or other surfaces. This lead distinguishes itself through increased strength and flexibility during the production, a very soft non-crumbling powder release during the application and the fact that it can be sharpened easily with standard sharpening devices.
This object is solved in that a copolymer is used as thickening agent, which contains polyoxyethyleneglycol-polymer (PEG) with 5 to 300 CH2xe2x80x94CH2xe2x80x94O monomers and also contains tetramethoxy-methylglycouril monomers. A copolymer of PEG-180 (q.v. [quod vide]=see previous), Dodoxynol-5, PEG-25-tristyrylphenol and tetramethoxymethylglycouril monomers is preferably used as thickening agent. According to the INCI1 nomenclature, this substance is also referred to as xe2x80x9cPolyether-1.xe2x80x9d The aforementioned copolymer component Dodoxynol-5 is PEG-5 dodecyl-phenylether.
1Translator""s Note: INCI=International Nomenclature of Cosmetic Ingredients 
Surprisingly, the use of associative thickening agents of this type not only has a thickening and emulsifying effect on the powdery components laced with water during the production, but also results in noticeably improved flexibility of the extruded lead ropes as well as uniform extrudability during the production as compared to the prior art. In the process, strength values can be achieved that match those of brittle and inflexible leads used for comparison, which contain bentonite (example V). By adding a very small amount of organic binder, e.g. sodium alginate, it is possible to nearly double the breaking strength without this reducing the mechanical properties such as very soft applicability, excellent sharpening ability and flexibility of the initially water-containing lead rope.
In particular polymethylmethacrylate and mica are suitable as powder-containing filler materials. Mica with a small share of silica added to it (0.5 to 7 weight %) is advantageously used. Mixtures of the aforementioned filler materials surprisingly have distinguished themselves through a very soft, powdery release and can be produced without problems. The starting materials mixed with water, in the simplest case referring to thickening agents and filler materials, can be processed into masses with a homogeneous distribution of the filler material particles. These masses keep their consistency even during the extrusion process, meaning there is no separation between the thickening agent phase and the solid-material phase. In general terms, a mixture of a filler material with essentially spherical particles and a filler material with platelet-shaped particles is used. Particularly good results are obtained with potash (muscovite).
Adding small amounts ( less than 10%) of clay, kaolin, talcum, magnesium myristate or calcium stearate in particular can influence the release of the mass during the application as well as the mechanical strength. Wetting agents such as disodium-laureth-sulfosuccinate (INCI name), for example, can be used as auxiliary substances for extruding the leads and as adhesion promoters. To improve the sliding ability during the application and to improve the adhesive strength of the powder, as well as to reduce the formation of fissures in the leads during the drying process, small amounts ( less than 10%) of waxes, fats, oils (e.g. castor oil) or emulsifiers can be added. Hydrogenated palm kernel glycerides, hydrogenated palm glycerides are listed as examples. Protective substances such as lanolin, aloe vera, tocopherol and others as well as preserving agents or aromatic substances can also be added.